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Children’s Physical Activity Drops From Age 9 to 15

Physical activity levels dropped sharply in a large group of American children between the ages of 9 and 15, according to a long-term study. By the age of 15, most failed to reach the daily recommended activity level.

The 2005 Dietary Guidelines for Americans recommends that children
and adolescents engage in at least 60 minutes of moderate to
vigorous physical activity (MVPA) on most, if not all, days of
the week. Examples of moderate physical activity include walking
briskly, dancing, swimming or bicycling on level terrain. Examples
of vigorous physical activity are jogging, high-impact aerobic
dancing, swimming continuous laps or bicycling uphill. A lack
of physical activity in childhood raises the risk for obesity
and the many health problems it can contribute to later in life,
including heart disease and diabetes.

To see whether children are meeting these recommendations,
a team led by Dr. Philip Nader at the University of California
San Diego used data collected for the Study of Early Child Care
and Youth Development, a long-term study of more than 1,000 children
from ethnically and economically diverse backgrounds that was
funded by NIH’s Eunice Kennedy Shriver National Institute
of Child Health and Human Development (NICHD).

The study collected information on various aspects of children’s
health and development. At age 9, the researchers recorded the
activity levels of more than 800 children for 4-7 days. Activity
was measured with an accelerometer, a device worn on the belt
that records movement. The children’s activity levels were
assessed again at ages 11, 12 and 15.

As reported in the July 16, 2008, Journal of the American
Medical Association, the children averaged roughly 3 hours
of MVPA on weekdays and weekends at age 9. By age 15, however,
they averaged only 49 minutes per weekday and 35 minutes per
weekend.

At ages 9 and 11, more than 90% of the children met the recommended
level of 60 minutes or more of MVPA each day. By age 15, however,
only 31% met the recommended level on weekdays, while 17% met
the recommended level on weekends. On average, boys were more
active than girls, spending 18 more minutes per weekday in MVPA
than girls, and 13 more minutes per day in MVPA on weekends.

This research highlights the need for action by families, communities,
schools, health care systems and governments to help encourage
physical activity as children get older. “Helping American
children maintain appropriate activity levels is a major public
health goal requiring immediate action,” said NICHD Director
Dr. Duane Alexander.

Nader said that local school systems can play a major role
by ensuring that children receive recess breaks and daily active
physical education. He added that local governments could also
help by providing safe biking and walking routes around schools.

“But parents don’t need to wait for big changes,” Nader
said. “Whenever possible, parents could encourage family
walks with their children. Even walking for as few as 15 minutes
a day would provide health benefits. On weekends, family outings
could be centered on longer walks or biking.”